diff --git a/expat/CMakeLists.txt b/expat/CMakeLists.txt
index a3e918b1..5769c749 100644
--- a/expat/CMakeLists.txt
+++ b/expat/CMakeLists.txt
@@ -761,63 +761,73 @@ if(EXPAT_BUILD_FUZZERS)
         endforeach()
     endforeach()
 
-    find_package(Protobuf REQUIRED)
+    # Note: OSS-Fuzz is stuck in Ubuntu 20.04 land with too-old libprotobuf-dev.
+    #       Until OSS-Fuzz arrives in the present with Ubuntu 24.04, we are not
+    #       building xml_lpm_fuzzer for -DEXPAT_OSSFUZZ_BUILD=ON for an actual
+    #       chance at a successful build in OSS-Fuzz' pipelines.  Related:
+    #       - https://github.com/google/oss-fuzz/issues/13016
+    #       - https://github.com/google/oss-fuzz/issues/11835
+    #       - https://github.com/google/oss-fuzz/pull/13018
+    #       - https://github.com/google/oss-fuzz/pull/13015
+    if(NOT EXPAT_OSSFUZZ_BUILD)
+        find_package(Protobuf REQUIRED)
 
-    # Only include libprotobuf-mutator here so we don't build it in non-fuzz
-    # configurations.
-    include(ExternalProject)
+        # Only include libprotobuf-mutator here so we don't build it in non-fuzz
+        # configurations.
+        include(ExternalProject)
 
-    set(ProtobufMutator_PREFIX libprotobuf-mutator)
-    set(ProtobufMutator_PATH ${CMAKE_CURRENT_BINARY_DIR}/${ProtobufMutator_PREFIX}/src/${ProtobufMutator_PREFIX})
-    set(ProtobufMutator_BUILD_PATH ${ProtobufMutator_PATH}-build)
-    set(ProtobufMutator_INCLUDE_DIR ${ProtobufMutator_PATH})
-    set(ProtobufMutator_LIBRARIES ${ProtobufMutator_BUILD_PATH}/src/libfuzzer/libprotobuf-mutator-libfuzzer.a ${ProtobufMutator_BUILD_PATH}/src/libprotobuf-mutator.a)
+        set(ProtobufMutator_PREFIX libprotobuf-mutator)
+        set(ProtobufMutator_PATH ${CMAKE_CURRENT_BINARY_DIR}/${ProtobufMutator_PREFIX}/src/${ProtobufMutator_PREFIX})
+        set(ProtobufMutator_BUILD_PATH ${ProtobufMutator_PATH}-build)
+        set(ProtobufMutator_INCLUDE_DIR ${ProtobufMutator_PATH})
+        set(ProtobufMutator_LIBRARIES ${ProtobufMutator_BUILD_PATH}/src/libfuzzer/libprotobuf-mutator-libfuzzer.a ${ProtobufMutator_BUILD_PATH}/src/libprotobuf-mutator.a)
 
-    ExternalProject_Add(
-        ${ProtobufMutator_PREFIX}
-        PREFIX ${ProtobufMutator_PREFIX}
-        GIT_REPOSITORY https://github.com/google/libprotobuf-mutator.git
-        GIT_TAG 75f1720aeb847b780f270ad7d4157ece5d4f3df1  # v1.4-8-g75f1720
-        CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-        CMAKE_CACHE_ARGS
-            -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
-            -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
-            -DLIB_PROTO_MUTATOR_EXAMPLES:BOOL=OFF
-            -DLIB_PROTO_MUTATOR_TESTING:BOOL=OFF
-        BUILD_BYPRODUCTS ${ProtobufMutator_LIBRARIES}
-        UPDATE_COMMAND true
-        INSTALL_COMMAND true)
+        ExternalProject_Add(
+            ${ProtobufMutator_PREFIX}
+            PREFIX ${ProtobufMutator_PREFIX}
+            GIT_REPOSITORY https://github.com/google/libprotobuf-mutator.git
+            GIT_TAG 75f1720aeb847b780f270ad7d4157ece5d4f3df1  # v1.4-8-g75f1720
+            CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
+            CMAKE_CACHE_ARGS
+                -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
+                -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
+                -DLIB_PROTO_MUTATOR_EXAMPLES:BOOL=OFF
+                -DLIB_PROTO_MUTATOR_TESTING:BOOL=OFF
+            BUILD_BYPRODUCTS ${ProtobufMutator_LIBRARIES}
+            UPDATE_COMMAND true
+            INSTALL_COMMAND true)
 
-    # Check for availability of protobuf compiler to avoid hard-to-understand
-    # errors from make(1) down the line as seen with CMake 3.25.1 on Debian
-    if(NOT Protobuf_PROTOC_EXECUTABLE)
-        message(SEND_ERROR
-            "The protobuf compiler (protoc) could not be found. "
-            "Is it installed and working properly?")
+        # Check for availability of protobuf compiler to avoid hard-to-understand
+        # errors from make(1) down the line as seen with CMake 3.25.1 on Debian
+        if(NOT Protobuf_PROTOC_EXECUTABLE)
+            message(SEND_ERROR
+                "The protobuf compiler (protoc) could not be found. "
+                "Is it installed and working properly?")
+        endif()
+
+        protobuf_generate_cpp(XML_LPM_FUZZER_PROTO_SRCS
+                            XML_LPM_FUZZER_PROTO_HDRS
+                            fuzz/xml_lpm_fuzzer.proto)
+
+        add_executable(xml_lpm_fuzzer
+                    fuzz/xml_lpm_fuzzer.cpp
+                    ${XML_LPM_FUZZER_PROTO_SRCS})
+        target_include_directories(xml_lpm_fuzzer PUBLIC ${ProtobufMutator_INCLUDE_DIR})
+        target_link_libraries(xml_lpm_fuzzer
+                            fuzzpat
+                            ${Protobuf_LIBRARIES}
+                            ${ProtobufMutator_LIBRARIES})
+        add_dependencies(xml_lpm_fuzzer ${ProtobufMutator_PREFIX})
+
+        # NOTE: Avoiding target_link_options here only because it needs CMake >=3.13
+        if(EXPAT_OSSFUZZ_BUILD)
+            set_target_properties(xml_lpm_fuzzer PROPERTIES LINK_FLAGS $ENV{LIB_FUZZING_ENGINE})
+        else()
+            target_compile_options(xml_lpm_fuzzer PRIVATE -fsanitize=fuzzer)
+            set_target_properties(xml_lpm_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
+        endif()
+        set_property(TARGET xml_lpm_fuzzer PROPERTY RUNTIME_OUTPUT_DIRECTORY fuzz)
     endif()
-
-    protobuf_generate_cpp(XML_LPM_FUZZER_PROTO_SRCS
-                          XML_LPM_FUZZER_PROTO_HDRS
-                          fuzz/xml_lpm_fuzzer.proto)
-
-    add_executable(xml_lpm_fuzzer
-                   fuzz/xml_lpm_fuzzer.cpp
-                   ${XML_LPM_FUZZER_PROTO_SRCS})
-    target_include_directories(xml_lpm_fuzzer PUBLIC ${ProtobufMutator_INCLUDE_DIR})
-    target_link_libraries(xml_lpm_fuzzer
-                          fuzzpat
-                          ${Protobuf_LIBRARIES}
-                          ${ProtobufMutator_LIBRARIES})
-    add_dependencies(xml_lpm_fuzzer ${ProtobufMutator_PREFIX})
-
-    # NOTE: Avoiding target_link_options here only because it needs CMake >=3.13
-    if(EXPAT_OSSFUZZ_BUILD)
-        set_target_properties(xml_lpm_fuzzer PROPERTIES LINK_FLAGS $ENV{LIB_FUZZING_ENGINE})
-    else()
-        target_compile_options(xml_lpm_fuzzer PRIVATE -fsanitize=fuzzer)
-        set_target_properties(xml_lpm_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
-    endif()
-    set_property(TARGET xml_lpm_fuzzer PROPERTY RUNTIME_OUTPUT_DIRECTORY fuzz)
 else()
     if(EXPAT_OSSFUZZ_BUILD)
         message(SEND_ERROR